heather: you know syrian president assad, he released some pictures, he released some video. i have, i believe we have some of that, that he says proves that rebel forces used chemical weapons on this attack. he alleges it happened on march 19th in aleppo. just from you viewing this video, taking a look at these pictures, can you yourself tell, i mean, you can't tell if chemical weapons were in fact used here but president assad says this is proof. >> well certainly doctors after a period of time would be able to determine that to be sure. whether we could get accurate information from assad's medical system i'm highly skeptical of it but you know there is some reservation here i think. if a assad was going to use chemical weapons you would think it would have some military value in the sense that damascus was under siege or aleppo was under siege and he was using those weapons as an act of desperation. also you can assume, heather, that our surveillance is watching those stockpiles. if in fact there are movements out of those stockpiles to tactical units which would be a ver